Conventionally, an optical-disk recording-reproduction apparatus has been used for recording and reproducing, for example, digital audio information that is digital information whose contents are consecutively recorded.
The optical-disk recording-reproduction apparatus has a construction, for example, as illustrated in FIG. 14, and conducts recording and reproduction. Upon recording, analog audio information is inputted through an input terminal 24, and converted into digital audio information in an A/D converter 14. The digital audio information is further converted into recording information in a recording-data processing circuit 11 so as to become suitable for recording, and is transmitted to a coil driver 5. Then, the coil driver 5 drives a coil 4 so that a modulated magnetic field corresponding to the recording information is applied to an optical disk 1.
Meanwhile, upon receipt of an instruction from a controller 16, a laser driver 6 allows an optical pickup 3 to project a light beam of high power onto the optical disk 1, and the temperature of the optical disk 1 is thus raised locally so as to allow desired information to be recorded thereon.
Upon reproduction, after information of a target recorded area has been extracted from a TOC memory 13, the optical pickup 3 is allowed to access to the area in question. Thus, the information, which was recorded on the optical disk 1, is read out by the optical pickup 3, and directed to a reproduced-data processing circuit 12 through a reproduction amplifier 7.
The reproduced-data processing circuit 12 converts the inputted information into digital audio information, and sends it to a D/A converter 15. The digital audio information is converted into analog audio information in the D/A converter 15, and released from an output terminal 25.
Instructions as to the recording and reproduction are entered through an operation section 17, and converted into control signals for various sections in the controller 16.
Further, the current positional information and operational state of the optical pickup 3 are displayed on a display section 18 under control of the controller 16.
However, in the information recording-reproduction method of the above-mentioned optical-disk recording-reproduction apparatus, for example, in the case of music information, both the read-out operation of a music program from the optical disk 1 that is conducted by the optical pickup 3 and the reproducing operation of the music program are carried out in real time. For this reason, upon switching music programs to be reproduced, the accessing operation of the optical pickup 3 has be be activated, thereby interrupting the reproducing operation for a while; this raises a problem of slow switching operation.
Moreover, when the user tries to recognize what music programs are recorded in the optical disk 1 by actually reproducing those music programs, he or she has to repeatedly give instructions to the optical-disk recording apparatus so as to access each of those music programs. This results in other problems, such as complicated operation and long-time operation.
In order to solve the former problem, the applicant of the present invention has filed Japanese Patent Application No. 9702/1992 (Tokuganhei 4-9702), which has suggested an improved information recording-reproduction method. In this method, a buffer memory is installed, and digital information on an optical disk, which is to be reproduced, is stored in the buffer memory beforehand, and a reproducing operation is then carried out based on the digital information stored in the buffer memory.
In the case when music programs are switched to start reproducing a different one, this information reproducing method provides a switching operation faster than that of the conventional method. For example, suppose that digital audio information of four seconds is converted into information of one second by using compression, and recorded in an optical disk. Upon reproduction, this method allows the optical pickup to read this information from the optical disk in one second, and makes it possible to reproduce audio sound for four seconds by using an information-decompression processing circuit. This means that the optical pickup has an inoperative time of three seconds, and another reading operation for different music programs may be carried out by using this spare time. Furthermore, in the case of again reproducing music programs once stored in the buffer memory, the switching time between the music programs is shortened because those music programs are directly reproduced from the buffer memory.
However, in the above-mentioned information reproducing method that has been suggested by the applicant of the present invention, when a certain music program, which is recorded on the optical disk, is to be reproduced for the first time, the music program in question has to be first stored in the buffer memory. At this time, the accessing operation of the optical pickup is activated; this results in a problem of slow switching operation because it is difficult to start reproducing the music program in question immediately.
Another problem with the conventional information reproduction method is that a large quantity of buffer memory is required since all music programs have to be stored in the buffer memory.